Write and compile source code on your Java J2ME mobile device. Develop C++, Java, PHP, and HTML code - With fully highlighted syntax. J2MEdit is the first and only tool that combines the power of a large programming IDE and the portability of a mobile phone to create a small and easy to use source code editor

Personal Mobile App - Create Mobile App in 2 minutes - Free. Guys, We have just launched a new MakePack(dot)com Mobile Application Creatot, where you can create personal Mobile app in less then 2 minutes

PhoneGap is an open source development tool for building fast, easy mobile applications with JavaScript.
If you are a web developer who wants to build mobile applications in HTML and JavaScript while still taking advantage of the core features in the iPhone, Android, Symbian and Blackberry SDKs, PhoneGap is for you

Libsssd is a cross-platform, integer-based audio library designed for interactive applications and games on small devices such as smartphones/PDAs
Libsssd currently supports Linux (OSS, ESD), Win32, WinCE Intent/AmigaDE (hosted), and Symbian S60

Mobile BASIC - Mobile BASIC is a BASIC interpreter for J2ME based Mobile Phones. It uses no special extensions and should be compatible with all J2ME mobile phones. BASIC program can be either created directly on the mobile or, for registered customers, using our web-site based development environment